The present invention relates to a manual paper feeder in an image forming apparatus such as a color plain paper copy machine (which will be abbreviated to PPC -Plane Paper Copy machine-) or a printer which prints and records information from an image information supplying apparatus such as a personal computer (which will be abbreviated to PC-Personal Computer-) or a digital camera on paper sheets such as manually supplied plain paper sheets or OHP sheets having different paper qualities and paper thicknesses.
In the manual paper feeder provided in an image forming apparatus for forming images on the paper sheets, various contrivances have been heretofore made in order to smoothly carry the manually supplied paper sheets to an image forming mechanism such as a photosensitive drum or a transfer roller. Any particular problem does not occur when the number of the manually inserted paper sheets is one, but when a plurality of paper sheets are superimposed on each other in a paper feed portion, the paper sheet to be normally supplied drags another paper sheet under the above paper sheet and it is inconveniently fed together with the lower paper sheet on occasion. As a countermeasure, various separation mechanisms for the paper sheets are provided in the next stage of the paper feed portion of the manual paper feeder, as disclosed in Japanese Patent No. 2655916, Japanese Utility Model Registration No. 2585428 and Japanese Utility Model Publication No. 24516/1991.
As the separation mechanism for the manual paper feeder, a combination of a frictional separation member made of a felt material and a rubber roller is used, but when a paper feed rubber roller having a high friction coefficient is used in order to give a carrying frictional force to the paper sheets to be carried, a friction coefficient xcexc1 between the paper feed rubber roller and the paper sheet to be carried and another friction coefficient xcexcp between the paper sheets to be carried are larger than a friction coefficient xcexc2 between the frictional separation member formed of a felt material and the paper sheet to be carried, so that the paper sheets to be carried cannot be separated from each other one by one and so the plurality of paper sheets are often fed together.
Furthermore, when the frictional separation member is formed of a rubber material in order to prevent the feeding of the plural paper sheets due to the above-described frictional separation member made of the felt material, a friction coefficient xcexc2xe2x80x2 between the frictional separation member made of the rubber material and the paper sheet to be carried is larger than the friction coefficient xcexcp between the paper sheets to be carried and the friction coefficient xcexc1 between the paper feed rubber roller and the paper sheet to be carried, so that there sometimes occurs a problem that the carrying frictional force deteriorates to cause a feeding failure.
In order to eliminate the above-described problem, an object of the present invention is to provide a manual paper feeder which can prevent the feeding of plural paper sheets or a feeding failure by enabling the variable adjustment of a frictional force between a paper feed roller and a frictional separation member.
To achieve the above object, a manual paper feeder according to a basic concept of the present invention is directed to a manual paper feeder attached to an image forming apparatus comprising at least an image data receiving portion and an image forming device, and this manual paper feeder comprises a manual feed unit for supplying a paper sheet mounted by a user; and a paper sheet release unit including at least a paper feed roller for carrying the paper sheet mounted in the manual feed unit; a frictional separation member for carrying the paper sheet by the frictional force while holding the manually supplied paper sheets between the frictional separation member itself and the paper feed roller; and a frictional force variable mechanism for changing the frictional force for holding the paper sheet between the paper feed roller and the frictional separation member.
Furthermore, a manual paper feeder according to a different aspect of the present invention is directed to a manual paper feeder attached to an image forming apparatus comprising at least an image data receiving portion and an image forming device, and this manual paper feeder comprises a manual feed unit for supplying paper sheets mounted by a user; and a paper sheet release unit including at least roller paper feeding means for carrying the paper sheets mounted in the manual feed unit; frictional separating means for carrying the paper sheets by the frictional force while holding the manually supplied paper sheets between the frictional separating means itself and the roller paper feeding means; and frictional force variable means for changing the frictional force for holding the paper sheet between the roller paper feeding means and the frictional separating means.